Transcript ppt

Botnets
Usman Jafarey
Including slides from The Zombie Roundup by Cooke,
Jahanian, McPherson of the University of Michigan
Botnet
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Collection of infected systems
Controlled by one party
Most commonly used Bot families
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Agobot
SDBot
SpyBot
GT Bot
Agobot
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Most sophisticated
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20,000 lines C/C++ code
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IRC based command/control
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Large collection of target exploits
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Capable of many DoS attack types
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Shell encoding/polymorphic obfuscation
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Traffic sniffers/key logging
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Defend/fortify compromised system
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Ability to frustrate dissassembly
SDBot
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Simpler than Agobot, 2,000 lines C code
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Non-malicious at base
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Utilitarian IRC-based command/control
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Easily extended for malicious purposes
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Scanning
DoS Attacks
Sniffers
Information harvesting
Encryption
SpyBot
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<3,000 lines C code
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Possibly evolved from SDBot
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Similar command/control engine
No attempts to hide malicious purposes
GT Bot
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Functions based on mIRC scripting capabilities
HideWindow program hides bot on local system
Port scanning, DoS attacks, exploits for RPC
and NetBIOS
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Variance in codebase size, structure, complexity,
implementation
Convergence in set of functions
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Possibility for defense systems effective across bot
families
Bot families extensible
Agobot likely to become dominant
Control
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All of the above use IRC for command/control
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Disrupt IRC, disable bots
Sniff IRC traffic for commands
Shutdown channels used for Botnets
IRC operators play central role in stopping
botnet traffic
Automated traffic identification required
Future botnets may move away from IRC
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Move to P2P communication
Traffic fingerprinting still useful for identification
Host control
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Fortify system against other malicious attacks
Disable anti-virus software
Harvest sensitive information
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PayPal, software keys, etc.
Economic incentives for botnets
Stresses need to patch/protect systems prior to
attack
Stronger protection boundaries required across
applications in OSes
Propagation
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Horizontal scans
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Vertical scans
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Fingerprinting to identify scans
Future methods
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Single IP across range of ports
Current scanning techniques simple
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Single port across address range
Flash , more stealthy
Source code examination
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Propagation models
Exploits/Attacks
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Agobot
 Has the most elaborate set
 Several scanners, various flooding mechanisms for DDoS
SDBot
 None in standard
 UDP/ICMP packet modules usable for flooding
 Variants include DDoS
SpyBot
 NetBIOS attacks
 UDP/TCP/ICMP SYN Floods, similar to SDBot
 Variants include more
GTBot
 RPC-DCOM exploits
 ICMP Floods, variants include UDP/TCP SYN floods
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Required for protection
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Future
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Host-based anti-virus
Network intrusion detection
Prevention signatures sets
More bots capable of launching multiple exploits
DDoS highlight danger of large botnets
Delivery
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Packers, shell encoders for distribution
Malware packaged in single script
Agobot separates exploits from delivery
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Exploit vulnerability
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Buffer overflow
Open shell on host
Upload binary via HTTP or FTP
Encoder can be used across multiple exploits
Streamlines codebase
NIDS/NIPS need knowledge of shell codes/perform
simple decoding
NIDS incorporate follow-up connection detection for
exploit/delivery separation prevention
Obfuscation
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Hide details of network transmissions
Only slightly provided by encoding
Same key used in encoding => signature matching
Polymorphism – generate random encodings, evades
signature matching
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Agobot
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POLY_TYPE_XOR
POLY_TYPE_SWAP (swap consecutive bytes)
POLY_TYPE_ROR (rotate right)
POLY_TYPE_ROL (rotate left)
NIDS/Anti-virus eventually need to develop protection
against polymorphism
Deception
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Detection evasion once installed
a.k.a. rootkits
Agobot
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Debugger tests
VMWare tests
Anti-virus process termination
Pointing DNS for anti-virus to localhost
Shows merging between botnets/trojans/etc.
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Honeynet monitors must be aware of VM attacks
Better tools for dynamic malware analysis
Improved rootkit detection/anti-virus as deception
improves